Arginase protein, crystal structure. human Arginase-1 enzyme in complex with an inhibitor. Arginase converts arginine into ornithine and urea, as part of the urea cycle. 3D rendering of trimeric arginase bound to an inhibitor; low-poly molecular surfaces of the protein chains are shown in blue. Molecular surfaces of the inhibitor are shown in yellow. The pink balls and lines are abstract decorative elements only.